Hello All,
I picked up a pretty nice 1995 Johnson 25 HP outboard motor a little while ago. It's been sitting for a while but it appears to have very low hours. It looked pretty nice but I gave it a "going over" just be sure. New plugs, cleaned the carb (new float, float valve assembly), fresh gas (50/1 mix), new fuel tank, new fuel line w/ bulb.
I put the boat in the water and the new motor runs GREAT!
Now here's the problem, if I idle for a while, like 10 minutes or so, maybe less, when I go to mash the throttle and run again the engine runs like crap in the mid to upper throttle ranges. It sputters and surges and the engine acts like it's going to jump off the back of the boat as long as I hold the throttle open. The boat won't even plane out. Squeezing the primer bulb or squirting that fuel spray thing does nothing. It's like someone is very rapidly going from idle to wide open throttle and back to idle over and over again. All linkages on the carb are operating fine, the butterfly is not wildly flapping. As soon as I slow back down to an idle or a high idle, it runs great again, just no mid to upper throttle. If I shut off the engine for a while, the problem goes away and the boat runs like normal again until I idle too long again. If I get up on plane and run her fast, she's happy and she'll run all day. I just can't idle for too long.
There's not much to these carbs, I've been through it twice now. The only adjustment is the low speed mixture and that has been adjusted well I think. I adjusted the float, it's fine. The upper speed orrifice appears to be fine, clean and well seated. I'm running out of things to check. Could it be something electrical? I doubt it but I won't rule it out. I've searched this site looking for others with similar problems but didn't see anything.
Any ideas guys?
Thanks
I picked up a pretty nice 1995 Johnson 25 HP outboard motor a little while ago. It's been sitting for a while but it appears to have very low hours. It looked pretty nice but I gave it a "going over" just be sure. New plugs, cleaned the carb (new float, float valve assembly), fresh gas (50/1 mix), new fuel tank, new fuel line w/ bulb.
I put the boat in the water and the new motor runs GREAT!
Now here's the problem, if I idle for a while, like 10 minutes or so, maybe less, when I go to mash the throttle and run again the engine runs like crap in the mid to upper throttle ranges. It sputters and surges and the engine acts like it's going to jump off the back of the boat as long as I hold the throttle open. The boat won't even plane out. Squeezing the primer bulb or squirting that fuel spray thing does nothing. It's like someone is very rapidly going from idle to wide open throttle and back to idle over and over again. All linkages on the carb are operating fine, the butterfly is not wildly flapping. As soon as I slow back down to an idle or a high idle, it runs great again, just no mid to upper throttle. If I shut off the engine for a while, the problem goes away and the boat runs like normal again until I idle too long again. If I get up on plane and run her fast, she's happy and she'll run all day. I just can't idle for too long.
There's not much to these carbs, I've been through it twice now. The only adjustment is the low speed mixture and that has been adjusted well I think. I adjusted the float, it's fine. The upper speed orrifice appears to be fine, clean and well seated. I'm running out of things to check. Could it be something electrical? I doubt it but I won't rule it out. I've searched this site looking for others with similar problems but didn't see anything.
Any ideas guys?
Thanks
